🧮Numble

Guess the hidden calculation in six tries. It is exactly eight characters long, made of the digits 0 to 9 and the symbols + − * / =.

• Every guess must itself be a true calculation, not just any arrangement of characters. 3+2*5=13 is a guess you can make; 3+2*5=25 is not, because it isn't correct.
• There is exactly one =, and only a plain number to the right of it, never another calculation.
• Standard order of operations applies: * and / are worked out before + and -. So 3+2*5 is 13, not 25.
• Division must come out exactly, and no number may start with a redundant zero.

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What the colours mean

After each guess every tile is coloured, the same idea as a word-guessing game:

• Green. That character is in the answer and in the right place.
• Purple. That character is in the answer, but somewhere else.
• Grey. That character is not in the answer at all.

Repeats are counted, not just matched. If your guess has two 1s and the answer has one, you get one colour and one grey.

Rearrangements count

If the answer is 10+20=30 then 20+10=30 wins too: addition and multiplication can be written either way round. Subtraction and division cannot, so those have to be in the right order. You can turn this off below if you would rather find the exact arrangement.

Playing

1. Tap the keys, or type on a keyboard. Enter submits. Backspace clears the square the caret is on, or steps back and clears the one before if that square is already empty, so tapping a square and pressing it deletes that character rather than its neighbour.
2. Tap any square to type into it, in any order. If you work out that the answer ends in =15, put that in first and fill the rest around it; squares can be left blank while you think. All eight are needed to submit.
3. A guess that isn't a correct calculation is refused and costs you nothing, so there is no penalty for checking your arithmetic on the board.
4. The keys colour themselves as you learn what is and isn't in the answer.